The present invention relates to a power supply voltage transition comparison circuit, a power supply voltage transition comparison method, and a semiconductor integrated circuit. For example, the present invention relates to a power supply voltage transition comparison circuit suitable for use in which a semiconductor integrated circuit is set to a test mode, a power supply voltage transition comparison method suitable for that use, and a semiconductor integrated circuit including the power supply voltage transition comparison circuit.
Test signal generation circuits for generating a test signal for setting a semiconductor integrated circuit such as a microcontroller to a test mode have been known. For example, a test signal generation circuit of a semiconductor device disclosed in Japanese Unexamined Patent Application Publication No. 4-147074 includes a high-voltage detection circuit, a counter, and a test signal latch. The high-voltage detection circuit determines whether or not a voltage higher than a normal power supply voltage is input to a first input terminal. The counter counts a clock signal that is input to a second input terminal while the voltage higher than the normal power supply voltage is input to the first input terminal. The test signal latch generates a test signal when the count number of the counter reaches a predetermined count number.
A test signal generation circuit of a semiconductor device disclosed in Japanese Unexamined Patent Application Publication No. 6-207971 includes a high-voltage detection circuit, a counter, and a test signal latch circuit. The high-voltage detection circuit determines whether or not a voltage higher than a normal power supply voltage is input to an input terminal, and outputs a high-voltage detection signal. The counter counts the high-voltage detection signal. The test signal latch circuit generates a test signal when the count number of the counter reaches a predetermined count number.
A test signal generation circuit disclosed in Japanese Unexamined Patent Application Publication No. 6-309475 includes first to third voltage comparators and a combinational logic circuit that logically processes the outputs of these comparators. The first voltage comparator compares a power supply voltage with a first reference voltage. The second voltage comparator compares the power supply voltage with a second reference voltage. The third voltage comparator compares the power supply voltage with a third reference voltage. The first reference voltage is higher than the second reference voltage, and the second reference voltage is higher than the third reference voltage. When the combinational logic circuit detects an output pattern that is output from the first to third comparators when a power supply voltage having a predetermined voltage waveform is input to the first to third comparators, the combinational logic circuit generates a test signal. When the test signal is generated, the circuit(s) to be tested is set to a test mode.